High-pressure metal halide discharge lamps of the type to which the present invention relates are used frequently in illumination systems for theater stages and for film and television studios. The light should have a color temperature of between 4000 and 9000 K. and excellent color rendition in all the color temperature ranges. Such lamps also are used in projection technology and in spot illumination, and especially where special light color illumination effects are desired.
The referenced U.S. Pat. No. 3,654,506 and British 1,376,509 describe mercury high-pressure discharge lamps which have halide additives. The halides used are dysprosium halide and/or holmium halide and/or thulium halide. These lamps provide light which has a spectral composition approximating daylight, with a color temperature of about 6000 K. The color rendition index Ra, however, does not have optimal values. Especially, the color rendition index R.sub.9 for red spectral ranges has at the most a value of the stage 3 of about 40. This is also true for most of the high-pressure discharge lamps of other types or fills on the market, also used for the purposes of the lamp of the present invention. It is of importance to provide for appropriate and correct illumination which correctly reproduces red hues, and particularly skin color. Such correct rendition of red hues is of particular importance when the light source is used for theater stages, film or television studios.